The transition of North Anatolian fault system in Sapanca Lake and its structural effects

ABSTRACT In this Master of Sciences Study, the eastern extension of North Anatolian Fault in Sapanca Lake and its effect on Lake morphology was investigated. Bathymetry and 3.5 kHz high-resolution seismic reflection data recorded on Sapanca Lake showed that subbottom layers of Sapanca Lake bottom is mainly consist of recent sedimentary units. Several surface faults can be identified in seismic reflection profiles and precisely mapped in bathymetric map. Because of acoustic masking effect of existing gas, the deeper extension of these faults could not be traced. Terrain modeling of Sapanca Lake showed that, at least three east west trending separate terraces (Gölbaşı, Çayağzı, Kazakburun) having slope <1° located between the Sapanca basin and northern shore. North Anatolian Fault seems a gradual transition zone connecting the lower Sapanca basin to higher terraces on northern slope. The eastern movement of Northern block of the Sapanca Lake is continuous. Southern slope and adjacent land area is the western directed segment of the North Anatolian Fault. Eastern Sapanca Lake basin has influenced by counterclockwise rotation and the depth contours show clear southeastward opening trend in this area. North Anatolian Fault, which enters to Sapanca Lake from western edge, fellows the Northern slope of the Lake basin and show a continuation trend below overlying thick sedimentary sequence at the eastern border of the basin. However there is no evidence found the surface effect of surface faulting on seismic reflection profiles recorded in the eastern part of the Lake. The seismic reflection profiles processed together with precise bathymetric data showed that the Sapanca Lake is a perfect model of early stage of a classic pull-apart basin and it provides a natural laboratory for understanding of pull-apart basins. Keywords : Sapanca Lake, Bathymetry, Seismic reflection, North Anatolian Fault, Pull-apart basin